1. Field of the Invention
This invention relates to a throttle valve control system for a four-cycle internal combustion engine, and to an engine and a vehicle incorporating the same. More particularly, the present invention relates a throttle valve control system for an engine in which throttle valves are operated by an actuator, and in which plural fuel injection valves and fuel lines are arranged between throttle bodies and the actuator. The present invention also relates to an engine and a to a vehicle incorporating the described throttle valve control system.
2. Description of the Background Art
There are several known throttle valve control systems for four-cycle internal combustion engines. An example of a throttle valve control system for a four-cycle internal combustion engine is disclosed in the Japanese Laid-open Patent document No. 2002-256900.
In a four-cycle internal combustion engine disclosed in Japanese Laid-open Patent document No. 2002-256900, an actuator for driving plural throttle valves is disposed on a side of plural fuel injection valves, and fuel lines for supplying fuel to the plural fuel injection valves are arranged at locations remote from the fuel injection valves to avoid interference with the actuator.
In the four-cycle internal combustion engine described in Japanese Laid-open Patent document No. 2002-256900, the fuel lines are arranged at the locations remote from the fuel injection valves. Therefore, the arrangement of the fuel injection valves is restricted by the fuel lines, and in some instances, is also affected considerably by the location and position of the actuator, so that the freedom of design layout in placement of the fuel injection valves is limited, leading to a potential problem that the performance of the engine may be affected.
If priority is given to the arrangement of the fuel injection valves at appropriate locations to avoid the above-mentioned problem, the fuel lines have to be extended and arranged detouring considerably, thereby raising another problem that the fuel lines become longer.
The present invention has been made to overcome such drawbacks of the existing throttle valve control systems for internal combustion engines. Accordingly, it is one of the objects of the present invention to provide a throttle valve control system for an internal combustion engine, which is free of such problems as those described above.